Candidate stellar occultations by large trans-Neptunian objects up to 2015

Assafin, M.; Camargo, J. I. B.; Martins, R. Vieira; Braga-Ribas, F.; Sicardy, B.; Andrei, A. H.; Neto, D. N. da Silva

doi:10.1051/0004-6361/201118349

Cited by 39 publications

(62 citation statements)

References 33 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Stellar occultations allow detection of very tenuous atmospheres and can provide accurate sizes and albedos 9,10,11,3,12 , so we embarked on a programme of predicting and observing occultations by (136472) Makemake, also known as 2005 FY 9 . The occultation of the faint star NOMAD 1181-0235723 (with magnitude m R 5 18.22, where NOMAD is the Naval Observatory Merged Astronomic Dataset) was predicted in 2010 by methods similar to those used to predict occultations by several large bodies 13 , but refined as shown in Supplementary Information section 1. We arranged a campaign involving 16 telescopes, listed in Supplementary Table 1.…”

mentioning

confidence: 99%

Albedo and atmospheric constraints of dwarf planet Makemake from a stellar occultation

Ortiz¹,

Sicardy²,

Braga-Ribas³

et al. 2012

Nature

Self Cite

100

View full text Add to dashboard Cite

Pluto and Eris are icy dwarf planets with nearly identical sizes, comparable densities and similar surface compositions as revealed by spectroscopic studies 1,2 . Pluto possesses an atmosphere whereas Eris does not; the difference probably arises from their differing distances from the Sun, and explains their different albedos 3 . Makemake is another icy dwarf planet with a spectrum similar to Eris and Pluto 4 , and is currently at a distance to the Sun intermediate between the two. Although Makemake's size (1,420 6 60 km) and albedo are roughly known 5,6 , there has been no constraint on its density and there were expectations that it could have a Plutolike atmosphere 4,7,8 . Here we report the results from a stellar occultation by Makemake on 2011 April 23. Our preferred solution that fits the occultation chords corresponds to a body with projected axes of 1,430 6 9 km (1s) and 1,502 6 45 km, implying a V-band geometric albedo p V 5 0.77 6 0.03. This albedo is larger than that of Pluto, but smaller than that of Eris. The disappearances and reappearances of the star were abrupt, showing that Makemake has no global Pluto-like atmosphere at an upper limit of 4-12 nanobar (1s) for the surface pressure, although a localized atmosphere is possible. A density of 1.7 6 0.3 g cm 23 is inferred from the data. Stellar occultations allow detection of very tenuous atmospheres and can provide accurate sizes and albedos 9,10,11,3,12 , so we embarked on a programme of predicting and observing occultations by (136472) Makemake, also known as 2005 FY 9 . The occultation of the faint star NOMAD 1181-0235723 (with magnitude m R 5 18.22, where NOMAD is the Naval Observatory Merged Astronomic Dataset) was predicted in 2010 by methods similar to those used to predict occultations by several large bodies 13 , but refined as shown in Supplementary Information section 1. We arranged a campaign involving 16 telescopes, listed in Supplementary Table 1. The occultation was successfully recorded from seven telescopes, listed in Table 1, at five sites. From the images obtained, we made photometric measurements as a function of time (light curves).The light curves of the occultation are shown in Fig. 1. Fitting synthetic square-well models to the light curves yielded the disappearance and reappearance times of the star (Table 1), from which we calculate one chord in the plane of the sky for each site (see Supplementary Information section 3). On the basis of analyses of the light curves, taking into account the cycle time between the images and the dispersion of the data, we deduce that there were no secondary occultations, so we can reject the existence of a satellite larger than about 200 km in diameter in the areas sampled by the chords. The result is consistent with a deep-image survey that did not find any satellites 16 . The chords can be fitted with two shape models (Fig. 2). Our preferred shape, which is compatible with our own and other observations (see Supplementary Information section 8), corresponds to an elliptical object ...

show abstract

mentioning

confidence: 99%

Albedo and atmospheric constraints of dwarf planet Makemake from a stellar occultation

Ortiz¹,

Sicardy²,

Braga-Ribas³

et al. 2012

Nature

Self Cite

100

View full text Add to dashboard Cite

show abstract

“…First, because the reduction was made with a consistent and precise stellar catalogue and with a robust astrometry (PRAIA, Assafin et al 2011). Second, besides recent observations, this consistent set of numerous and precise positions covers many orbital periods at many distinct orbital plane sights, allowing to fully constrain the orbit for the short time span explored in this work.…”

Section: Orbit Computationsmentioning

confidence: 99%

New orbits of irregular satellites designed for the predictions of stellar occultations up to 2020, based on thousands of new observations

Gomes-Júnior

Assafin

Desmars

et al. 2016

Mon. Not. R. Astron. Soc.

Self Cite

View full text Add to dashboard Cite

Gomes -Júnior et al. (2015) published 3613 positions for the 8 largest irregular satellites of Jupiter and 1787 positions for the largest irregular satellite of Saturn, Phoebe. These observations were made between 1995 and 2014 and have an estimated error of about 60 to 80 mas. Based on this set of positions, we derived new orbits for the eight largest irregular satellites of Jupiter: Himalia, Elara, Pasiphae, Carme, Lysithea, Sinope, Ananke and Leda. For Phoebe we updated the ephemeris from Desmars et al. (2013) using 75% more positions than the previous one. Due to their orbital characteristics, it is common belief that the irregular satellites were captured by the giant planets in the early Solar System, but there is no consensus for a single model explaining where they were formed. Size, shape, albedo and composition would help to trace back their true origin, but these physical parameters are yet poorly known for irregular satellites. The observation of stellar occultations would allow for the determination of such parameters. Indeed Jupiter will cross the galactic plane in 2019-2020 and Saturn in 2018, improving a lot the chances of observing such events in the near future. Using the derived ephemerides and the UCAC4 catalogue we managed to identify 5442 candidate stellar occultations between January 2016 and December 2020 for the 9 satellites studied here. We discussed how the successful observation of a stellar occultation by these objects is possible and present some potential occultations.

show abstract

“…This set of initial predictions must be complete, that is, must contain all possible events of a given TNO that involves stars up to a given magnitude, and must be accurate enough to allow for selecting of those for which observational efforts to refine the initial prediction are worth employing. All initial predictions of stellar occultations to the objects presented in Table 4, with the exception of (2060) Chiron and (60558) Echeclus, are detailed in Assafin et al (2012) and Camargo et al (2014) and are based on observations made at La Silla (Chile) with the ESO 2.2 m telescope that is equipped with the Wide Field Imager (WFI).…”

Section: Offset Observationsmentioning

confidence: 99%

“…For the initial predictions given by both Assafin et al (2012) and Camargo et al (2014), corrections to ephemerides were done by considering an average offset, which was determined by the position differences in the sense "observation minus ephemeris". As mentioned earlier in the text, this kind of correction (offset) was assumed to be constant until a new one is determined on the basis of newer observations.…”

Section: Offset Observationsmentioning

confidence: 99%

See 1 more Smart Citation

Orbit determination of trans-Neptunian objects and Centaurs for the prediction of stellar occultations

Desmars

Camargo

Braga-Ribas

et al. 2015

A&A

Self Cite

View full text Add to dashboard Cite

Context. The prediction of stellar occultations by trans-Neptunian objects (TNOs) and Centaurs is a difficult challenge that requires accuracy both in the occulted star position and in the object ephemeris. Until now, the most used method of prediction, involving dozens of TNOs/Centaurs, has been to consider a constant offset for the right ascension and for the declination with respect to a reference ephemeris, usually the latest public version. This offset is determined as the difference between the most recent observations of the TNO/Centaur and the reference ephemeris. This method can be successfully applied when the offset remains constant with time, i.e. when the orbit is stable enough. In this case, the prediction even holds for occultations that occur several days after the last observations. Aims. This paper presents an alternative method of prediction, based on a new accurate orbit determination procedure, which uses all the available positions of the TNO from the Minor Planet Center database, as well as sets of new astrometric positions from unpublished observations. Methods. Orbits were determined through a numerical integration procedure called NIMA, in which we developed a specific weighting scheme that considers the individual precision of the observation, the number of observations performed during one night by the same observatory, and the presence of systematic errors in the positions. Results. The NIMA method was applied to 51 selected TNOs and Centaurs. For this purpose, we performed about 2900 new observations in several observatories (European South Observatory, Observatório Pico dos Dias, Pic du Midi, etc.) during the 2007-2014 period. Using NIMA, we succeed in predicting the stellar occultations of 10 TNOs and 3 Centaurs between July 2013 and February 2015. By comparing the NIMA and Jet Propulsion Laboratory (JPL) ephemerides, we highlight the variation in the offset between them with time, by showing that, generally, the constant offset hypothesis is not valid, even for short time scales of a few weeks. Giving examples, we show that the constant offset method cannot accurately predict 6 out of the 13 observed positive occultations that have been successfully predicted by NIMA. The results indicate that NIMA is capable of efficiently refining the orbits of these bodies. Finally, we show that the astrometric positions given by positive occultations can help to refine the orbit of the TNO and, consequently, the future predictions. We also provide unpublished observations of the 51 selected TNOs and their ephemeris in a usable format by the SPICE library.

show abstract

Candidate stellar occultations by large trans-Neptunian objects up to 2015

Cited by 39 publications

References 33 publications

Albedo and atmospheric constraints of dwarf planet Makemake from a stellar occultation

Albedo and atmospheric constraints of dwarf planet Makemake from a stellar occultation

New orbits of irregular satellites designed for the predictions of stellar occultations up to 2020, based on thousands of new observations

Orbit determination of trans-Neptunian objects and Centaurs for the prediction of stellar occultations

Contact Info

Product

Resources

About